A team of biologists has discovered how 18 species of parasitic wasps can hunt in the same tiny patch of rainforest without needing to compete with one another.

The victims of the sadistic Bellopius wasp face one of the grisliest fates imaginable. The female wasp hunts down a helpless, infantile fruit fly and stabs it with her spear-like genitals—implanting it with a wasp egg. The wasp egg hatches inside the fly. The newborn wasp waits patiently until its host reaches adulthood, then devours the still-living fly from the inside out and—boom—bursts out of its chest, Alien-style.

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But as shocking the parasitic wasp's modus operandi is, a group of scientists led by Marty Condon at Cornell College has just discovered something just as weird about wasps and their prey—there is an insane number of both of them, all living in the exact same place. In an experiment published this week in journal Science, Condon discovered that on the flowers of two closely related plants in a small patch of the Peruvian Amazon, 18 species of the nightmarish wasps co-exist and hunting their fruit fly prey side-by-side. And oddly enough, the species of flies were just as abundant.

This makes no sense at first glance. With even just two species of wasps (or flies) in a small area, one should be outcompeting the other in the competition to be the most efficient killer (or the best escapist, in the case of the flies.) "So we figured there would be just one wasp that would just hit every baby fly down the line in this niche," Condon says. "I was blown away."

For the study, these researchers gathered 1500 adolescent fruit flies from the flowers—dissecting and genetically testing half to search for implanted wasps, and carefully watching the other half to see if (or what) wasps emerged from them. Only then could Condon and her colleagues see just what was going on. As it turns out, although all the closely related bugs are sharing the same tiny nook of the rainforest, each wasp species seems incapable of parasitizing more than a single species of fly.

In the rare occasion that a wasp mistakenly injects an egg into the wrong species of fly, Condon found that somehow the fly manages to annihilate the wasp egg inside it. While Cordon's team found genetic evidence of the wrong wasp inside their dissected flies, they never managed to catch one bursting out alive.

"My guess as to how the flies protect themselves against most of the wasps is through some type of immune reaction, but we don't exactly know," Cordon says. "Other fruit flies have specialized cells that could basically smother the baby wasps, or it could have something to do with viruses injected along with the wasp egg." Whatever the cause, the flies' internal defenses allowed both kinds of insects to evolve an amazing level of diversity right next to one another.

Susan Swensen Witherup, a biologist at Ithaca College who was not involved in the research, insists that the Cordon discovery highlights more than just an interesting insect phenomenon. For biologists seeking to understand the evolution of parasites and their prey, Cordon's finding adds an extra layer of complexity. "Physical escape, like to a new plant species, is one option for these flies. But it appears there's another way to internally escape their predators, and that's adding a whole other dimension to the diversification of this species," she says.